Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L21/00—Compositions of unspecified rubbers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
  • B29C67/24—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 characterised by the choice of material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
  • C08J3/247—Heating methods
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/30—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by mixing gases into liquid compositions or plastisols, e.g. frothing with air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J15/00—Sealings
  • F16J15/02—Sealings between relatively-stationary surfaces
  • F16J15/06—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces
  • F16J15/10—Sealings between relatively-stationary surfaces with solid packing compressed between sealing surfaces with non-metallic packing
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2307/00—Characterised by the use of natural rubber
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
  • Y10S264/13—Cell size and distribution control while molding a foam

Definitions

• Patented Dec. 9, 1947 METHOD OF PRODUCING BETICULATED STRUCTURES Joseph A. Talalay, New Haven, Conn.
• This invention relates to procedure for obtaining a cellular structure of rubber or the like and to the product obtained by such procedure, and especially to the coagulation or gelaticn of a foamed aqueous dispersion of rubber or the like.
• the chief objects of my invention are to avoid disadvantages such as those above mentioned; to obtain a stereoreticulate product of small and uniform pore size; and to obtain a product in r 2 age of foam with the concurrent weakening of the cell walls and the consequent fusion of smaller bubbles into larger ones (which is the mechanism by virtue of which foam degenerates on standing). Consequently much finer, more uniform and stronger foam-rubbers can be made bymy method compared with foam-rubber made usin delayed action chemical coagulants.
• the time from the start to the completion of the coagulation is very short (and in some instances instantaneous). It is a recognized fact that better foam-rubbers are obtained when the time span of the sol-gel transformation is short.
• neoprene latex Type 571 will irreversibly coagulate in a foam layer onehalf inch thick at a temperature of C. in about twenty minutes.
• Natural rubber latex on the other hand, will not have irreversibly coagulated in a similar foam thickness until the temperature has been lowered to 50 or -60 C. and the time of exposure to cold extended to perhaps thirty minutes.
• the foam is cooled to the moderate freezing temperature quickly.
• the rapid drop in the temperature of the foamed dispersion is accompanied by a rapid increase in viscosity. This in turn arrests the detrimental natural ⁇ drainties of the foam-rubber.
• the water is the active part of the latex in the first step of formation of a foam-ice.
• Foamice is formed regardless of the nature of the elastomer at any temperature below the freezing point of water, e. g., in 5-10 minutes at --20 C. or --25' 0., and in a correspondingl longer time at say 10 C.
• a strong and firm gel is required.
• the gel must be highly cohesive.
• a gel coagulated with a strong coagulant, such as an alcohol, or an acid, is much firmer than gels obtained by delayed action coagulants or by freezing alone.
• the coagulation (gelation) of a latex with a delayed action coagulant takes place at a pH near the iso-electric point (pH 6.5 to 7.5, dependent on the nature of the elastomer latex). It has been the experience that the foam loses considerably in foam stability when the latex approaches the iso-electric point, and unless especially fortified and protected by soaps and viscoslfying agents the foam tends to collapse just at the point when it is about to be gelled. ff'his problem does not exist in my process, in which the foam is (to use a medical analogy) "anaesthetized by the freezing of the occluded water while tion is performed.
• frozen latex coagulates to a tough continuous film upon contact with strong coagulants, while liquid (not frozen) latex would curdle and fiocculate under the same circumstances.
• the conversion of the still reversible (re-meltable) ice-foam" to the irreversible latex-gelthe gelling operafoam can according to my invention be effected in a. few seconds orin a very few minutes by any of the following steps.
• the ice;-foam"- is immersed into a bath of coagulating fiuid, such as ethyl-alcohol, acetone, solution of calcium chloride or calcium nitrate in water, 81001101201 acetone, aqueous solutions of coagulating electrolytes, acids, etc., and upon immersion int such a solution instantaneous coagulation occurs without any damage to the foam structure.
• coagulating fiuid such as ethyl-alcohol, acetone, solution of calcium chloride or calcium nitrate in water, 81001101201 acetone, aqueous solutions of coagulating electrolytes, acids, etc.
• a coagulating gas such as sulphur dioxide, carbon dioxide, nitri oxide, hydrochloric acid, etc., or'to vapors of acoagulating liquid, examples being nitrogen or carbon dioxide saturated with alcohol vapor.
• the mold After about five minutes the mold is transferred into a steam vulcanizer where it is heated for about 25 minutes at 260 F. in live steam.
• the vulcanized foam-article is removed from the mold. washed, centrifugally extracted and dried.
• the invention is applicable to aqueous dispersions of synthetic rubbers as well as natural rubber latex or artificial dispersions of natural rubber, and such dispersions are intended to be included in the expression aqueous dispersion of rubber" in the appended claims, as are also aqueous dispersions of reclaimed rubber and of elastomers in general.
• the preliminary formation of the foam can be effected by any of the known procedures, such as mechanical whipping or beating. chemical gas generation, or physical release of gas or vapor.
• the foam may be produced in association with, or brought into association with, reinforcing fibers or other compounding materials.
• the coagulating fluid or gas can be made to circulate through the mold with the aid of an external propulsion element such as a pump, and can also be withdrawn by evacuation after they have accomplished the work of coagulating the ice-foam to an irreversible structure.
• the coagulation can be combined with the vulcanization by permeating the frozen structure with a mixture of sulphur dioxide and hydrogen sulphide.
• a mixture of sulphur dioxide and hydrogen sulphide When catalyzed by the moisture present in the cell walls the two gases react, forming active sulphur, and produce vulcanization at low temperature simultaneously with the coagulation.
• the gases are preferably admitted simultaneously into a partially or fully evacuated mold, but they also can be used successively.
• Emample. -165 grams of natural rubber latex, centrifuged or creamed to a concentration of 60%. are stabilized with 5 grams of a 20% solutlon of potassium oleate soap, and are now compoundedwith a paste' containing 5 g. of zinc oxide, 2 g. of sulphur, -1 to 2 g. of an antioxidant,
• the mixture Before the mixture has substantially expanded it is poured into an aluminum mold of an internal volumeof 1000 c. c. and permitted to expand therein to fill the mold.
• the mold is now immersed into a bath of calcium chloride brine (maintained at 30 0.) for a period 5 minutes.
• the method of making a stereoreticulate structure which comprises first producing and then irreversibly coagulating a foamed aqueous dispersion of rubber, the coagulation being efiected by freezing the foam and thereby converting it into a stereoreticulate structure defining an intercommunicating system of flow channels and thereafter passing a coagulant, from its exterior, into the interstices of the frozen structure.
• the methodof making a stereoreticulate structure which comprises first producing and then irreversibly coagulating a foamed aqueous dispersion of rubber, the coagulation being effected by freezing the foam and thereby converting it into a stereoreticulate structure defining an intercommunicating system of flow channels and thereafter passing a coagulant, from its exterior, into the interstices of the frozen structure, the foam being cooled only to such moderately low temperature and for such moderate length of time as would not of itself cause irreversible coagulation of the foam.
• the method of making a stereoreticulate structure which omprises first producing and then irreversibly coagulating a foamed aqueous dispersion of rubber, the coagulation being efiected by, freezing the foam and thereby converting it into a stereoreticulate structure defining an intercommunicating system of fiow channels and thereafter passing a coagulant, from its exterior, into the interstices of the frozen structure, the method including the step of applying suction to the reticulated structure to withdraw fluid from its interstices.
• the method of making a stereoreticulate structure which comprises first producing and the foam has frozen to ice, but the latex is still then irreversibly coagulating a foamed aque- 'ous dispersion of rubber, the coagulation being effected by freezing the foam and thereby converting it into a stereoreticulate structure defining an intercommunicating system of flow channels and thereafter passing a coagulant, from its exterior, into the interstices of the frozen structure, the foam' being subjected to a relatively low temperature to freeze it quickly and then, before 5 coagulation is completed, to a temperature that is higher than the first mentioned temperature but lower than the melting point of the foam.
• the method of making a stereoreticulate structure which comprises first producing and then irreversibly coagulating a foamed aqueous dispersion of rubber, the coagulation bein effected by freezing the foam and thereby converting it into a. stereoreticulate structure defining an intercommunicating system of flow chan nels and thereafter passing a coagulant, from its exterior, into the interstices of the frozen structure, the foam being held to determinate external size and shape while thus treated, and the method including the step of efiecting a permanent setting of the coagulated substance in that shape.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Priority Applications (6)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24796760

Family Applications (1)

Country Status (6)

Cited By (34)

Families Citing this family (1)

Citations (4)

• 0
  • GB GB619619D patent/GB619619A/en active Active
  • NL NL68275D patent/NL68275C/xx active
• 1946
  • 1946-09-11 US US696365A patent/US2432353A/en not_active Expired - Lifetime
• 1947
  • 1947-05-28 FR FR947281D patent/FR947281A/fr not_active Expired
  • 1947-09-03 CH CH263988D patent/CH263988A/de unknown
• 1948
  • 1948-11-16 DE DEP21857A patent/DE818855C/de not_active Expired

Patent Citations (4)

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